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Repository research at GRS: from radionuclide to repository concept

The Repository Research Centre of GRS in Braunschweig (Source: GRS)By the year 2040, around 29,000 m³ of high-active waste and about 270,000 m³ of medium- and lo-active waste will have accrued in Germany. This waste originates mostly from nuclear power plants, but also from industrial, medical and research applications. In Germany, the construction and operation of repositories for radioactive waste are the responsibility of the federation state. Here, GRS provides support at two levels: by repository safety research and by repository safety assessments for licensing procedures.

The scientists and authorised experts at GRS look at the issue of disposal from the points of view of the chemical properties of the individual radioactive isotopes up to the technical concepts of repository systems stretching over several kilometres. At the GRS Repository Research Centre in Braunschweig, they acquire fundamental knowledge about the processes developing in a repository and develop methods for assessing the long-term safety of a repository. The disposal of hazardous chemical waste in so-called underground waste disposal sites is also a research topic at GRS Braunschweig. Scientists prepare and analyse saline solutions in the accredited geoscientific laboratory of GRS (Source: GRS)The researchers want to find answers to the question of how the waste can be lastingly stored in a safe manner. What could a repository for radioactive waste look like? What kinds of rock are suitable for storage? How will a repository evolve over a million years?

Experimental research at the GRS laboratory
At the geoscientific laboratory of GRS, the experts carry out application-oriented fundamental research. They perform geochemical and geotechnical experiments or take and analyse samples – e.g. saline solutions as encountered in repositories or underground waste disposal sites. Apart from that, the geoscientific laboratory staff also carry out analyses, e.g. of gas samples from the Asse mine as part of the fact-finding work (cf. EPROM).In 2013, the laboratory was accredited as test laboratory for the sampling and chemical analysis of saline solutions. On top of that, part of the Repository Research Division of GRS is also an accredited inspection agency for issues relating to the origin of saline solutions, the leaching of contaminants from waste, and the conversion of concrete materials.

Geotechnical analysis of different rock samples in a pilot plant (Source: GRS)In-situ research in underground laboratories
Examinations that are carried out in laboratories deep below ground supplement the research in the geoscientific laboratory. The geological and structural conditions in an underground laboratory are similar to those in a repository. The experiments that are performed here are therefore particularly well-suited for extrapolation to a repository. GRS is involved in a number of large-scale international experiments carried out in underground laboratories in France, Sweden and Switzerland.

Models, computer programs, simulations
The researchers at GRS use the results of the experimental research as a basis for modelling. With such models it is possible to describe theoretically the relevant processes, e.g. the transport of gas in a repository for radioactive waste or in an underground waste disposal site for hazardous chemical waste. These models in turn form the basis of computer codes with which the processes can be calculated and simulated. GRS employs such codes for predicting the safety of repositories over very long periods of time. They are an important tool in the preparation and assessment of repository concepts or for the comparison of repositories in different host rock types.

Virtual model of an underground laboratory in 360-degree representation at the Fraunhofer IFF. Decision-making processes become easier if all involved can visualise the details. (Source: Dirk Mahler/ Fraunhofer IFF)
Virtual underground laboratory VIRTUS
Together with other research institutions, GRS is currently in the process of developing the world’s first virtual underground research laboratory. With this new tool, researchers will be able to carry out virtual experiments in detailed models of repository mines in real geological formations. As the processes can be visualised in 3D animation, the software can also be used to inform the general public about the issue of disposal in a more comprehensible and transparent manner.